This is pretty cool 
. I created something very similar using a Flask webserver hosted on Heroku. It accepts the payload from Plex using Plex’s Webhooks feature. Depending on the Plex client that triggered the webhook I send certain event’s into HomeAssistant using HA’s web api. I have a few automations triggered off of those events, mostly dimming/brightening lights if I’m watching plex in my living room after the sun has gone down.
Do you expose your node server to the outside world? The reason I ask is because one major benefit of using Plex Webhooks over Tautulli, is that the Webhooks fire regardless of which Plex server you’re watching content on. Tautulli can only see your Plex activity on the Plex server that it’s monitoring. The consistency and speed that Plex Webhooks allow for is really nice. If your node server wasn’t accessible to the outside world and you were watching content off of a friend’s Plex server that server would try to POST to the URL in your Webhook settings and it would fail. Though I suppose it doesn’t matter if you only watch content on your own Plex server and that server is on your network.
Plex On!